This invention relates to image reproduction apparatus and has its most important application in the making of original microfilm from light reflecting hard copy (such as printed documents and the like), or from the light patterns produced on the faces of a cathode ray tube used in computer readout systems and the like.
Microform, such as microfilm, heretofore has been produced, in the main, by one of three processes, namely the diazo process, the silver halide process and the vesicular process. All of these microfilm making processes share one, or more, disadvantages, chief among which are relatively long exposure and/or development times, the complexity and/or inconvenience in the materials and equipment required to develop the film and in the poor quality of the enlarged microfilm image produced thereby. The vesicular process has the added disadvantage of very poor latent image stability which requires immediate development after exposure. A recently developed microfilm making process referred to as the dry silver process, is one which requires short exposure time and is developed rapidly by application of heat. However, this process like the other referred to microfilm making processes, has resolution and contrast limitations which usually produce relatively poor quality readable copy when the microfilmed images are enlarged to full size.
The silver halide process uses silver halide films responsive primarily to visible light which reflects readily on light surfaces and is absorbed to a substantial degree by opaque inks. The diazo and vesicular films used in the diazo and vesicular processes are primarily responsive to ultraviolet radiation which does not reflect efficiently, if at all, from the materials used to make printed documents. Moreover, in comparison to silver halide films, which have a very high degree of sensitivity to visible light, diazo and vesicular films have a low degree of photosensitivity, even to ultraviolet radiation.
The most widely used process for producing original microfilm of a printed document uses a camera to take a picture of the visible light reflected from the document upon silver halide film through a microfilm reducing lens which produces about a 24 to 1 or greater image reduction on the silver halide film. Since only a small percentage of the initially projected visible light is actually directed after reflection to the lens, only a highly photosensitive material like silver halide was thought to be practical for making original microfilm from printed documents. However, the images obtained on silver halide microfilm have low contrast and poor edge definition and resolution due to the granular character of the silver halide emulsions and the film must be processed with special chemicals to impart archival properties to the finished product. Moreover, development of silver halide film requires the typical complex and time consuming developing process well-known in the art. This complexity of the developing process and the equipment used and the skilled personnel who operate the same are such that development is usually done by special film processing companies. Thus, the silver halide film development process requires of the order of at least tens of seconds to carry out development of the exposed film material and employs short-lived developing chemicals, which are unpredictable, and which due to surface phenomena, are absorbed and absorb on the surface of the film substrate to an extent such that drying of the developed sheet material is difficult. The nature of the process, therefore, requires a skilled operator to carry it out.
Microfilm copies are generally made by making contact copies of the original microfilm upon less expensive diazo or vesicular film. The low contrast and poor edge definition of the original silver halide film is transferred to the diazo or vesicular microfilm copies which are generally of comparably less or inferior quality as compared to the original microfilm. Upon enlargement of the microfilm image in a microfilm reader or the like, the poor contrast and edge acuity of the original microfilm produce marginally acceptable enlarged microfilm images. As previously indicated, while the dry silver process film would greatly reduce the complexity of the developing procedure, the contrast and resolution deficiencies referred to would also be present, and where microfilm copies are to be made therefrom would involve a higher film cost than diazo and vesicular films.
To expand further on the deficiencies of the heretofore commonly used diazo and vesicular microfilm copying processes, the following additional facts should be kept in mind. The diazo microfilm copying process, which is perhaps the most widely used process, is based on the formation of a dye as a result of the reaction of a diazo compound with its decomposition product or with a coupling component. While basically a low cost process, the diazo process has a number of important disadvantages, including the necessity, generally, for utilizing aqueous or gaseous ammonia as the developer for the exposed sheet material. Apart from its obnoxious properties, the use of aqueous or gaseous ammonia in the process requires special equipment to insure uniform distribution of ammonia vapor in the developing chamber, and to prevent the accumulation of any condensed ammonia vapors therein. Precautions, also, must be taken to prevent escape of ammonia vapors in the work area. Even then, ammonia vapors are invariably sensed in the work area. Over and above the foregoing considerations, the process requires expensive machinery with long path lengths to carry out development of the exposed sheet material, and, in addition, requires development times of the order of at least tens of seconds. Apart from these shortcomings, images produced by the diazo process have low contrast, a severe limitation especially in microfilm where, due to the requirement for considerable enlargement in readout, the highest possible contrast is needed. Furthermore, images produced by the diazo process tend to fade when exposed to light, and, therefore, are not permanent.
The vesicular developing process, also, is a complex process. Thus, for example, the vesicular film is first given an overall pre-exposure sensitization. This is followed by an image-wise exposure and heating which, because of the poor latent image stability of vesicular film materials must be developed in a matter of seconds after exposure. Finally, a post-exposure fix is required. Development of the exposed sheet material requires temperatures in the range of 120.degree. C to 140.degree. C to bring about expansion of nitrogen gas released by a diazo component during exposure of the sheet material. Due to the relatively high development temperatures employed, vesicular films require the use of more costly, heat stable substrates. Heat also acts to erase the image and, therefore, suitable procautions must be taken to protect the developed film from heat during storage and use, a factor which detracts from the archival qualities of the film. Images obtained by the process have inferior edge acuity, limited resolution and relatively low contrast, and a contrast which is dependent upon the aperture system used.
It is well known that the poor quality of the image produced on microfilm reading equipment has made it an uncomfortable and laborious process to obtain information in this manner. Also, the aforementioned difficulties in the processing of the various exposed microfilm materials heretofore commercially utilized have been at least partly responsible for the absence of office microfilm making equipment which develops as well as exposes the microfilm in a manner which permits the operation thereof by unskilled personnel, so that enlarged projected copies of microfilmed records becomes immediately available shortly after exposure of the microfilm thereto. While diazo and vesicular films have some cost and processing advantages over silver halide films, they have not been used to make original microfilms, as previously indicated because of the fact that they cannot effectively respond to reflected visible or invisible light from printed documents. Additionally, they have such poor photosensitivity even to ultraviolet light that they have not been seriously considered for making microforms where high recording rates become desirable.
Accordingly, a main object of the invention is to provide a unique microform producing apparatus and a method of making original microform of printed documents or cathode ray tube traces directly on relatively poorly photosensitive materials providing images of high resolution and excellent edge definition.
Another object of the invention is to provide a microform producing apparatus as described which is for office or laboratory use by unskilled office personnel to make completely processed microform reductions, especially microfilm reductions, of printed documents or cathode ray tube trace images without the necessity for outside processing of the film. A related object of the invention is to provide an apparatus and method as just described where exposure and processing rates are so rapid that the interval between successive exposures can be substantially under ten seconds and the processing of each exposed frame thereof takes at most a few seconds.
Another object of the invention is to provide an apparatus and method of making original microfilm of printed documents or cathode ray tube traces which apparatus and method utilize relatively inexpensive films (i.e. film containing no precious metals like silver and the like), which film utilizes materials which normally require long exposure times to convert the same to film transparencies which fabricated in the usual way, but are utilized in a unique manner where they produce microform images with exposure times of at most a few seconds.
Another object of the invention is to provide an apparatus and method as above described where the contrast, resolution and acuity of the microfilm produced thereby is so much improved over the microfilm heretofore made that microform recorded images can be easily read on microfilm readers.
A further object of the invention is to provide an apparatus and method as above described which makes maximum use of already developed reproduction equipment.
A still further object of the invention is to provide apparatus as described which can be manufactured to sell or lease at a reasonable cost, is reliable in operation and can be serviced and maintained at a reasonable cost.